MM_Any.pm - deal with license discrepancy between META.yml and Makefile.PL

Detect if the generated license metadata from Makefile.PL is different
from that in the META.yml and warn about it. Also do not complain about
it being "unknown" when in fact it is being overiden by the META.yml file.

Author: demerphq

lib/ExtUtils/MM_Any.pm

@@ -1184,6 +1184,8 @@ sub _fix_metadata_before_conversion {
 
     return unless _has_cpan_meta;
 
+    my $generated_metadata = $self->{generated_metadata};
+
     my $bad_version = $metadata->{version} &&
                       !CPAN::Meta::Validator->new->version( 'version', $metadata->{version} );
     # just delete all invalid versions
@@ -1236,13 +1238,27 @@ sub _fix_metadata_before_conversion {
         $meta = bless $metadata, 'CPAN::Meta';
     }
 
+
+    my $gen_license;
+    $gen_license = $generated_metadata->as_struct({version => 2})->{license}
+        if $generated_metadata;
     my $now_license = $meta->as_struct({ version => 2 })->{license};
-    if ($self->{LICENSE} and $self->{LICENSE} ne 'unknown' and
-        @{$now_license} == 1 and $now_license->[0] eq 'unknown'
-    ) {
-        warn "Invalid LICENSE value '$self->{LICENSE}' ignored\n";
+
+    if ($self->{LICENSE} and $self->{LICENSE} ne 'unknown') {
+        if (@{$now_license} == 1 and $now_license->[0] eq 'unknown') {
+            if (!$gen_license or (@{$gen_license} == 1 and $gen_license->[0] eq "unknown")) {
+                warn "Invalid LICENSE value '$self->{LICENSE}' ignored\n";
+            } else {
+                $meta->{license}= $generated_metadata->{license};
+            }
+        }
+        if ($gen_license and $now_license and "@$gen_license" ne "@$now_license") {
+            warn "Your META.yml has a different license (@$now_license) than your Makefile.PL (@$gen_license)\n";
+        }
     }
 
+    $self->{generated_metadata} ||= $meta;
+
     $meta;
 }